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Discussion Starter · #1 ·
I have a completely stock 09 GT with its sad excuse for an exhaust system. I'm wanting to install the high flow cats for their performance increase, but I'm worried that these will make any future cat-back that I may want to install way too loud for my purposes. Now, don't get me wrong, I do love a good, loud "all hell breaking loose" exhaust at the track, but am wanting to stay very mild for my daily driver.

Would just the addition of the HFCs to my stock GT exhaust give me any enhancement in sound? I'm really wanting the mildest/still aggressive exhaust possible...

Question for those with any first-hand experience: Which is louder on a GT? GXP mufflers with solo HFC, or stock cats with solo mach balanced?

Thanks!
 

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Per Solo, you will see a 10-15 percent increase in volume as well as a deeper tone and more "burble" on the deceleration. Now Im not sure if that carries over to the stock GT exhaust system, but running there catback or axle back the increase can be expected. I havent heard a car with Solo HFC's that i didnt like the sound of, regardless of the system thats behind them.
 

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Discussion Starter · #3 ·
Thanks, yeah I read that as well but just wasn't sure if that held true with the stock GT exhaust. From what I've seen on youtube, these mufflers seem to kill just about any increase in sound even from headers as if they have magical powers.
 

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I've got solo HFC after the stock manifolds with a solo mach balanced with their resonators. I wanted it mild and its probably 25% louder than stock with a great tone and I can still leave the neighbourhood without waking up everyone. Put your foot into it though and it sounds great IMO. The stock cats are very restrictive so the solo's will free up your airflow but those huge cans and resonators on the stock exhaust would muzzle most of the increase in noise.
 

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every village has one
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Buy them. You won't be disappointed.
 

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I started with solo axel backs, then added an xpipe. A few months later I added the hfc's and its only loud if you floor it. It sounds great if driving slow. I was going to do mid length headers but it didn't seem to be much different from what I read with people doing the HFCs. They are worth it, they will give you some sound but they are well worth the increase in flow.
 

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Adding our high flow converters will get about 10-15% more volume overall, more on the outside than on the inside. If you have one of our kits, the J pipes are still effective in keeping out unwanted drone with the HF cats. The tone will also become a bit deeper as well. The HF cats are also direct bolt on, and come with everything you need for install, including the 02 extenders that keep the CEL off. (we designed them...they are not a generic extender)
 

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Mack
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I've got solo HFC after the stock manifolds with a solo mach balanced with their resonators. I wanted it mild and its probably 25% louder than stock with a great tone and I can still leave the neighbourhood without waking up everyone. Put your foot into it though and it sounds great IMO. The stock cats are very restrictive so the solo's will free up your airflow but those huge cans and resonators on the stock exhaust would muzzle most of the increase in noise.
Well said. My SOLO brings a smile to my face every time I turn the car on and/or give it some gas ;) I had eventually planned to go with a set of SOLO HFC's also but got a great deal on a used set of Kooks mids instead and will be getting them mounted hopefully soon. Good luck OP in your choice.
 

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I started with solo axel backs, then added an xpipe. A few months later I added the hfc's and its only loud if you floor it. It sounds great if driving slow. I was going to do mid length headers but it didn't seem to be much different from what I read with people doing the HFCs. They are worth it, they will give you some sound but they are well worth the increase in flow.
You don't happen to have a video of your exhaust do you? I have solo axle backs and x pipe and was thinking of doing hfc's as well.


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... Hi Flo Cats made a huge difference to my performance and sound increase,I have an
X Pipe and a set of Red Back Mufflers from Australia..factory mids are in the trash...no drone quiet driving but stand on it and heads turn...like the exhaust guy said.."Flo is Good"
 

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If my car wasnt being fixed I'd make a few short videos of daily drive by and more stuff. Ill do it whenever i get my csr back. But here's a decent reference. Kooks LTs - Solo HFCs - Solo Mach

https://www.youtube.com/watch?v=ia8DnS2Apyc&feature=youtube_gdata_player

In this video the phone is about ten feet away, and the idle is noticeable but not overbearing. Revs it sounds wicked, but then goes back to calm idle.

Here's cabin noise during WOT.

https://www.youtube.com/watch?v=OxtdYlbq4eg&feature=youtube_gdata_player

For the record the car had zero drone up to 74-76mph depending on the road surface. But even the drone above 76 is barely noticeable with the radio on.

Honestly, I'd recommend their hfcs. I went from stock to this, I didn't piece it together but solo is top notch, plus if you go FI your safe, each hfc is good for 6L of flow so no worrying about melting them. Plus the mach exhaust is the most docile of their systems. So if you get hfc and decide you want to rid the stock gt system you've got many options.

Hope I helped alittle.

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Discussion Starter · #12 ·
Thanks everyone! I actually ended up getting a great deal on some new kooks mids, so that's the direction I will be going! Can't wait to get them installed.

My bank account is struggling thanks to the month and a half I've owned this car haha.
 
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